In the image above the ruler is measuring in centimeters. The blue cylinder falls somewhere between 2.7cm and 2.8cm according to the ruler. Since we can estimate the last digit I would say that the length of the cylinder is 2.76cm. Since I am estimating any number 2.72cm or 2.78cm could also be correct. Why would 2.755 not be a correct measurement according to estimating the last digit?

The accuracy of the measuring ruler is given as tenth of a centimetre and given that the image above the ruler is measuring in between a tenth of a centimetre, it is therefore measuring at a higher accuracy than the ruler

The least count of the vernier scale =  (Main scale's smallest reading)/(Number of vernier scale divisions)

Where;

Main scale's smallest reading = 0.1 cm

Number of vernier scale divisions = 10

We have;

The least count of the vernier scale =0.1/10 = 0.01

The image above the ruler, (the vernier scale measurement) should therefore measure at hundredth of a centimetre and the value of the measurement given to two places of decimal, 2.XX, as such 2.755 which is of a level of accuracy of a thousandth for the vernier scale would not be correct.

Explanation: